Re: [Xen-devel] [PATCH v6] xen/arm: Allow balooning working with 1:1 memory mapping

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2013-12-17 at 14:55 +0000, Stefano Stabellini wrote:
> On Tue, 17 Dec 2013, Julien Grall wrote:
> > With the lack of iommu, dom0 must have a 1:1 memory mapping for all
> > these guest physical address. When the ballon decides to give back a
> > page to the kernel, this page must have the same address as previously.
> > Otherwise, we will loose the 1:1 mapping and will break DMA-capable
> > devices.
> > 
> > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > Cc: Keir Fraser <keir@xxxxxxx>
> 
> Acked-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>

Keir, any objections to this patch?

> 
> 
> >     Release: This is a bug that prevents DMA-capable devices to work after
> >     a guest has started.
> > 
> >     Changes in v6:
> >         - Use # instead of 0x
> >         - Make sure that d is evaluated in is_domain_direct_mapped
> >     Changes in v5:
> >         - Export dom0_11_mapping and transform is_domain_direct_mapped in 
> > macro
> >         - Add ifndef in common code to define is_domain_direct_mapped
> >     Changes in v4:
> >         - Fix typoes
> >         - Update comment in the code
> >     Changes in v3:
> >         - Remove spurious page = NULL
> >         - Rename is_dom0_mapped_11 to is_domain_direct_mapped
> >         - Coding style
> >     Changes in v2:
> >         - Drop CONFIG_ARM and add is_dom0_mapped_11
> > ---
> >  xen/arch/arm/domain_build.c  |    2 +-
> >  xen/common/memory.c          |   35 ++++++++++++++++++++++++++++++++++-
> >  xen/include/asm-arm/domain.h |    3 +++
> >  3 files changed, 38 insertions(+), 2 deletions(-)
> > 
> > diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> > index faff88e..47b781b 100644
> > --- a/xen/arch/arm/domain_build.c
> > +++ b/xen/arch/arm/domain_build.c
> > @@ -22,7 +22,7 @@
> >  static unsigned int __initdata opt_dom0_max_vcpus;
> >  integer_param("dom0_max_vcpus", opt_dom0_max_vcpus);
> >  
> > -static int dom0_11_mapping = 1;
> > +int dom0_11_mapping = 1;
> >  
> >  #define DOM0_MEM_DEFAULT 0x8000000 /* 128 MiB */
> >  static u64 __initdata dom0_mem = DOM0_MEM_DEFAULT;
> > diff --git a/xen/common/memory.c b/xen/common/memory.c
> > index eb7b72b..51f11ff 100644
> > --- a/xen/common/memory.c
> > +++ b/xen/common/memory.c
> > @@ -29,6 +29,10 @@
> >  #include <xsm/xsm.h>
> >  #include <xen/trace.h>
> >  
> > +#ifndef is_domain_direct_mapped
> > +# define is_domain_direct_mapped(d) ((void)(d), 0)
> > +#endif
> > +
> >  struct memop_args {
> >      /* INPUT */
> >      struct domain *domain;     /* Domain to be affected. */
> > @@ -122,7 +126,29 @@ static void populate_physmap(struct memop_args *a)
> >          }
> >          else
> >          {
> > -            page = alloc_domheap_pages(d, a->extent_order, a->memflags);
> > +            if ( is_domain_direct_mapped(d) )
> > +            {
> > +                mfn = gpfn;
> > +                if ( !mfn_valid(mfn) )
> > +                {
> > +                    gdprintk(XENLOG_INFO, "Invalid mfn %#"PRI_xen_pfn"\n",
> > +                             mfn);
> > +                    goto out;
> > +                }
> > +
> > +                page = mfn_to_page(mfn);
> > +                if ( !get_page(page, d) )
> > +                {
> > +                    gdprintk(XENLOG_INFO,
> > +                             "mfn %#"PRI_xen_pfn" doesn't belong to the"
> > +                             " domain\n", mfn);
> > +                    goto out;
> > +                }
> > +                put_page(page);
> > +            }
> > +            else
> > +                page = alloc_domheap_pages(d, a->extent_order, 
> > a->memflags);
> > +
> >              if ( unlikely(page == NULL) ) 
> >              {
> >                  if ( !opt_tmem || (a->extent_order != 0) )
> > @@ -270,6 +296,13 @@ static void decrease_reservation(struct memop_args *a)
> >               && p2m_pod_decrease_reservation(a->domain, gmfn, 
> > a->extent_order) )
> >              continue;
> >  
> > +        /* With the lack for iommu on some ARM platform, domain with 
> > DMA-capable
> > +         * device must retrieve the same pfn when the hypercall
> > +         * populate_physmap is called.
> > +         */
> > +        if ( is_domain_direct_mapped(a->domain) )
> > +            continue;
> > +
> >          for ( j = 0; j < (1 << a->extent_order); j++ )
> >              if ( !guest_remove_page(a->domain, gmfn + j) )
> >                  goto out;
> > diff --git a/xen/include/asm-arm/domain.h b/xen/include/asm-arm/domain.h
> > index 28d39a0..e2202a6 100644
> > --- a/xen/include/asm-arm/domain.h
> > +++ b/xen/include/asm-arm/domain.h
> > @@ -86,6 +86,9 @@ enum domain_type {
> >  #define is_pv64_domain(d) (0)
> >  #endif
> >  
> > +extern int dom0_11_mapping;
> > +#define is_domain_direct_mapped(d) ((d) == dom0 && dom0_11_mapping)
> > +
> >  struct vtimer {
> >          struct vcpu *v;
> >          int irq;
> > -- 
> > 1.7.10.4
> > 



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